Pmt1 mannosyl transferase is involved in cell wall incorporation of several proteins in Saccharomyces cerevisiae.
We constructed hybrid proteins containing a plant alpha-galactosidase fused to various C-terminal moieties of the hypoxic Srp1p; this allowed us to identify a cell wall-bound form of Srp1p. We showed that the last 30 amino acids of Srp1p, but not the last 16, contain sufficient information to signal glycosyl-phosphatidylinositol anchor attachment and subsequent cell wall anchorage. The cell wall-bound form was shown to be linked by means of a beta1,6-glucose-containing side-chain. Pmt1p enzyme is known as a protein-O-mannosyltransferase that initiates the O-glycosidic chains on proteins. We found that a pmt1 deletion mutant was highly sensitive to zymolyase and that in this strain the alpha-galactosidase-Srp1 fusion proteins, an alpha-galactosidase-Sed1 hybrid protein and an alpha-galactosidase-alpha-agglutinin hybrid protein were absent from both the membrane and the cell wall fractions. However, the plasma membrane protein Gas1p still receives its glycosyl-phosphatidylinositol anchor in pmt1 cells, and in this mutant strain an alpha-galactosidase-Cwp2 fusion protein was found linked to the cell wall but devoid of beta1,6-glucan side-chain, indicating an alternative mechanism of cell wall anchorage.
Bourdineaud
J P
JP
Laboratoire de Physiologie Moléculaire et Cellulaire, IBGC, Centre National de la Recherche Scientifique, Bordeaux, France.
van der Vaart
J M
JM
Donzeau
M
M
de Sampaïo
G
G
Verrips
C T
CT
Lauquin
G J
GJ
D001692:Biological Transport / Q000502:physiology; D015153:Blotting, Western; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D005696:Galactosidases / Q000032:analysis; D004693:Glucan Endo-1,3-beta-D-Glucosidase / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000502:physiology; D008364:Mannosyltransferases / Q000737:chemistry* / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D028901:alpha Karyopherins
D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D009687:Nuclear Proteins; D028901:alpha Karyopherins; D008364:Mannosyltransferases; C082696:protein O-mannosyltransferase; D005696:Galactosidases; D004693:Glucan Endo-1,3-beta-D-Glucosidase